A depletion problem of valuable metal mineral resources that is being issued recently is expected to hinder development of human civilization in the near future.
The yield of land lithium mineral resources with economy is only about 4,100,000 tons globally, and therefore the lithium mineral resources are scarce resources that will be depleted in the next 10 years.
The lithium resources excessively concentrate on some countries. Therefore, a method for mining lithium from an ore and a salt lake may not be applied realistically in Korea having an infinitesimal quantity of lithium reserves, and so on.
However, even though lithium is present in dissolved resources in sea water as a tiny quantity of 0.17 mg/L, it has been known that an overall dissolved quantity of lithium is considerable as 230 billion tons.
Therefore, a mineral-recovery technology capable of selectively extracting only specific valuable metal ions melted (dissolved) in sea water can lower overseas dependency for resources and stably supply resources, and as a result is a very important technology that has sufficient values as growth engine of the national economy and achieves the continuous development of the national economy.
Most of the related arts associated with a technology for recovering valuable metals from sea water have been developed, focusing on technologies for exchanging and adsorbing ions of inorganic or organic materials to selectively remove specific metal ions.
In particular, the valuable metals are generally recovered by a technology of embedding inorganic compound particles, such as manganese oxides, as a lithium ion molecular sieve in a polymer such as polyvinyl chloride (PVC) or storing them in a storage formed of a polymer membrane to selectively exchange ions and then perform acid treatment process.
The related arts as described above are advantageous in having a high recovery rate of lithium ion from sea water.
However, the related arts take much time to adsorb specific ions, and therefore have low economical efficiency and efficiency and the related arts need to use toxic materials such as acid in post-processing processes of recovering ions such as a process of isolating ions, and therefore cause a problem of corrosion of a system, environmental pollution, etc.
To solve the problem, Korean Patent No. 10-1136816 was proposed by the inventors of the present application.
The technology includes an electrode module to which metal ions such as lithium are adsorbed and moves a solution in which metal ions are present to the electrode module using a pump to adsorb lithium ion to the electrode module to which an electrode is applied.
Further, the technology may change polarity of the electrode to isolate lithium ion from the electrode module when intending to isolate the adsorbed lithium ion, thereby recovering lithium included in a solution such as sea water.
Meanwhile, the existing technology of recovering lithium from sea water is performed at deep sea owing to limited performance of an adsorbent, has big trouble in commercialization owing to enormous construction costs and operating costs of a system to recover lithium from sea water, has a short driving time because days of good weather conditions are rare, and has a safety problem due to typhoon, strong waves, etc.